Genus Homo was first published in the magazine Super Science Stories for March, 1941.
A busload of men and women are buried under a tunnel cave-in and are frozen in a state of suspended animation. After unknown ages they awake to a very strange and different world. Theu are the only surviving members of the human race or Genus Homo. The land is completely changed, new mountains where there were cornfields, vast forests replace barren flatlands.
And the animals... harmless little mammals have become huge mankillers but the biggest change is that the simians - gorillas, baboons, monkeys and the rest have become the civilized races of this new world.